The field end windings of a generator, motor, condenser, or other rotating electrical device are supported by a retaining ring fitted over the rotor. The inner diameter of the retaining ring is less than the outer diameter of the rotor in the range of 40 to 50 mils. The assembly is accomplished by sliding the retaining ring over the rotor by heating the retaining ring for a shrink fit with the rotor. Heat shrinking the retaining ring to the rotor can damage the insulation of the field end windings or the retaining ring itself or both. A centering ring is then fitted into a central bore of the retaining ring. The retaining ring and the rotor cannot be keyed to one another because of the retaining ring's inability to withstand the stresses encountered.
When a rotating electrical device is disassembled for maintenance or repair, the retaining ring must be heated in order to remove it from the rotor. Because of the required heavy shrink fit of the retaining ring to the rotor, it is difficult and costly to supply the heat necessary for disassembly. The insulation of the windings can be damaged during this process. With excessive heat, the retaining ring itself may be damaged. In the prior art, when a retaining ring is partially damaged because of stress corrosion, a cylindrical intermediate spacer ring has been inserted between the salvaged retaining ring and the rotor. But due to fit-up problems associated with the retaining ring, the cylindrical intermediate spacer ring, and the rotor, the retaining ring is completely replaced with a new retaining ring instead of being salvaged Also due to tolerance variance of the rotor, retaining rings are usually customized Also, because of the necessity of applying heat to retaining rings for both assembly and disassembly, repairs to rotating electrical devices at remote locations, such as ships at sea for example, are especially difficult to perform.
Hubs that are not provided with a keyway receive torque from the shaft through friction, so that the hubs must grip the shaft tightly. This gripping can be accomplished by advancing a tapered hub onto a tapered shaft a specified distance. Advancement by conventional mechanical means requires bracing the shaft, which, because of the great axially directed force needed to force on the hub, can cause damage to or buckling of the shaft In order to avoid bracing the shaft, the advance of the hub onto the shaft can be facilitated by expansion of the bore of the hub. Two methods are used most often: heating or hydraulic pressure. Drive coupling manufacturers have developed procedures for both mounting and dismounting tapered hubs onto and from tapered shafts by hydraulic means devoid of the application of heat. During either the mounting or dismounting procedure, oil under high pressure is pumped between the shaft and the hub through a high pressure feed oil line located in either the hub or the shaft to a shallow circular groove machined in either in the hub or in the shaft. O-rings are installed on both sides of the groove to trap the oil during the pressurizing procedure. A high pressure oil pump is connected to an inlet hole for the feed oil line provided in either the center of the shaft or the outside diameter of the hub. By a combination of an installation tool and the application of the high pressure oil so as to expand the bore of the hub, either the assembly or the disassembly of a retaining ring to or from a rotor can thus by accomplished by mechanical means devoid of application of heat to the hub.
The above described methods of assembly and disassembly cannot be applied to assembling or disassembling a retaining ring to or from a rotating electrical device rotor not only because of the difficulty of tapering the rotor but primarily because the winding slots of the rotor are open at the circumferential surface of the rotor with the result that the pressurized oil would enter the winding slots.